@Article{IPB-1134, author = {Abel, S. and Ticconi, C.A. and Delatorre, C.A.}, title = {{Phosphate sensing in higher plants}}, year = {2002}, pages = {1 - 8}, journal = {Plant Physiology}, volume = {115}, } @Article{IPB-1294, author = {Laskowski, M.J. and Dreher, K.A. and Gehring, M. and Abel, S. and Gensler, A. and Sussex, I.M.}, title = {{FQR1, a novel primary auxin-response gene, encodes an FMN-binding quinone reductase.}}, year = {2002}, pages = {578-686}, journal = {Plant Physiology}, url = {http://www.plantphysiol.org/content/128/2/578.abstract?sid=3f1f8a7a-ed15-40f3-9d7f-723ae31566f1}, volume = {128}, abstract = { FQR1 is a novel primary auxin-response gene that codes for a flavin mononucleotide-binding flavodoxin-like quinone reductase. Accumulation of FQR1 mRNA begins within 10 min of indole-3-acetic acid application and reaches a maximum of approximately 10-fold induction 30 min after treatment. This increase in FQR1 mRNA abundance is not diminished by the protein synthesis inhibitor cycloheximide, demonstrating thatFQR1 is a primary auxin-response gene. Sequence analysis reveals that FQR1 belongs to a family of flavin mononucleotide-binding quinone reductases. Partially purified His-tagged FQR1 isolated fromEscherichia coli catalyzes the transfer of electrons from NADH and NADPH to several substrates and exhibits in vitro quinone reductase activity. Overexpression of FQR1 in plants leads to increased levels of FQR1 protein and quinone reductase activity, indicating that FQR1 functions as a quinone reductase in vivo. In mammalian systems, glutathione S-transferases and quinone reductases are classified as phase II detoxification enzymes. We hypothesize that the auxin-inducible glutathioneS-transferases and quinone reductases found in plants also act as detoxification enzymes, possibly to protect against auxin-induced oxidative stress.} } @Article{IPB-355, author = {Vigliocco, A. and Bonamico, M.B. and Alemano, S. and Miersch, O. and Abdala, G.}, title = {{Activation of jasmonic acid production in Zea mays L. infected by the maize rough dwarf virus-Río Cuarto. Reversion of symptoms by salicylic acid}}, year = {2002}, pages = {369-374}, journal = {Biocell}, volume = {26(3)}, } @Article{IPB-1145, author = {Wang, Q. and Grubb, C.D. and Abel, S.}, title = {{Direct analysis of single leaf disks for chemopreventive glucosinolates}}, year = {2002}, pages = {152 - 157}, journal = {Phytochem Anal}, doi = {10.1002/pca.636}, url = {http://onlinelibrary.wiley.com/doi/10.1002/pca.636/abstract}, volume = {13}, abstract = {Natural isothiocyanates, produced during plant tissue damage from methionine-derived glucosinolates, are potent inducers of mammalian phase 2 detoxification enzymes such as quinone reductase (QR). A greatly simplified bioassay for glucosinolates based on induction and colorimetric detection of QR activity in murine hepatoma cells is described. It is demonstrated that excised leaf disks of Arabidopsis thaliana (ecotype Columbia) can directly and reproducibly substitute for cell-free leaf extracts as inducers of murine QR, which reduces sample preparation to a minimum and maximizes throughput. A comparison of 1 and 3 mm diameter leaf disks indicated that QR inducer potency was proportional to disk circumference (extent of tissue damage) rather than to area. When compared to the QR inducer potency of the corresponding amount of extract, 1 mm leaf disks were equally effective, whereas 3 mm disks were 70% as potent. The QR inducer potency of leaf disks correlated positively with the content of methionine-derived glucosinolates, as shown by the analysis of wild-type plants and mutant lines with lower or higher glucosinolate content. Thus, the microtitre plate-based assay of single leaf disks provides a robust and inexpensive visual method for rapidly screening large numbers of plants in mapping populations or mutant collections and may be applicable to other glucosinolate-producing species.} } @Article{IPB-1146, author = {Grubb, C.D. and Gross, H.B. and Chen, D.L. and Abel, S.}, title = {{Identification of Arabidopsis mutants with altered glucosinolate profiles based on isothiocyanate bioactivity}}, year = {2002}, pages = {143 - 152}, journal = {Plant Sci}, doi = {10.1016/S0168-9452(01)00550-7}, url = {http://www.sciencedirect.com/science/article/pii/S0168945201005507}, volume = {162}, abstract = {Glucosinolates are a diverse class of nitrogen- and sulfur-containing secondary metabolites. They are rapidly hydrolyzed on tissue disruption to a number of biologically active compounds that are increasingly attracting interest as anticarcinogenic phytochemicals and crop protectants. Several glucosinolate-derived isothiocyanates are potent chemopreventive agents that favorably modulate carcinogen metabolism in mammals. Methylsulfinylalkyl isothiocyanates, in particular the 4-methylsulfinylbutyl derivative, are selective and potent inducers of mammalian detoxification enzymes such as quinone reductase (QR). Cruciferous plants including Arabidopsis thaliana (L.) Heyhn, synthesize methylsulfinylalkyl glucosinolates, which are derived from methionine. Using a colorimetric assay for QR activity in murine hepatoma cells and high performance liquid chromatography (HPLC) analysis of desulfoglucosinolates, we have demonstrated a strong positive correlation between leaf QR inducer potency and leaf content of methionine-derived glucosinolates in various A. thaliana ecotypes and available glucosinolate mutants. In a molecular genetic approach to glucosinolate biosynthesis, we screened 3000 chemically mutagenized M2 plants of the Columbia ecotype for altered leaf QR inducer potency. Subsequent HPLC analysis of progeny of putative mutants identified six lines with significant and heritable changes in leaf glucosinolate content and composition.} } @Article{IPB-347, author = {Abdala, G. and Castro, G. and Miersch, O. and Pierce, D.}, title = {{Changes in jasmonate and gibberellin levels during development of potato plants (Solanum tuberosum)}}, year = {2002}, pages = {121-126}, journal = {Plant Growth Reg.}, volume = {36}, } @Article{IPB-1300, author = {Abel, S. and Theologis, A.}, title = {{A polymorphic bipartite motif signals nuclear targeting of early auxin- inducible proteins related to PS-IAA4 from pea (Pisum sativum)}}, year = {1995}, pages = {87-96}, journal = {Plant Journal}, url = {http://onlinelibrary.wiley.com/doi/10.1046/j.1365-313X.1995.08010087.x/abstract}, volume = {8}, abstract = { The plant hormone, indoleacetic acid (IAA), transcriptionally activates two early genes in pea, PS-IAA4/5 and PS-IAA6, that encode short-lived nuclear proteins. The identification of the nuclear localization signals (NLS) in PS-IAA4 and PS-IAA6 using progressive deletion analysis and site-directed mutagenesis is reported. A C-terminal SV40-type NLS is sufficient to direct the β-glucuronidase reporter to the nucleus of transiently transformed tobacco protoplasts, but is dispensible for nuclear localization of both proteins. The dominant and essential NLS in PS-IAA4 and PS-IAA6 overlap with a bipartite basic motif which is polymorphic and conserved in related proteins from other plant species, having the consensus sequence (KKNEK)KR-X(2471)-(RSXRK)/(RK/RK). Both basic elements of this motif in PS-IAA4, (KR-X41-RSYRK), function interdependently as a bipartite NLS. However, in PS-IAA6 (KKNEKKR-X36-RKK) the upstream element of the corresponding motif contains additional basic residues which allow its autonomous function as an SV40-type monopartite NLS. The spacer-length polymorphism, X(2470), in respective bipartite NLS peptides of several PS-IAA4-like proteins from Arabidopsis thaliana does not affect nuclear targeting function. The structural and functional variation of the bipartite basic motif in PS-IAA4-like proteins supports the proposed integrated consensus of NLS.} } @Article{IPB-1301, author = {Abel, S. and Nguyen, M.D. and Theologis, A.}, title = {{The PS-IAA4/5-like family of early auxin-inducible mRNAs in Arabidopsis thaliana}}, year = {1995}, pages = {19093-19099}, journal = {Journal of Biological Chemistry}, url = {http://www.jbc.org/content/270/32/19093.abstract?sid=c17d6e17-db5e-4424-8236-1c3dccb9ded2}, volume = {270}, abstract = { 1-Aminocyclopropane-1-carboxylic acid (ACC) synthase is the key regulatory enzyme in the biosynthetic pathway of the plant hormone ethylene. The enzyme is encoded by a divergent multigene family in Arabidopsis thaliana, comprising at least five genes, ACS1-5 (Liang, X., Abel, S., Keller, J. A., Shen, N. F., and Theologis, A.(1992) Proc. Natl. Acad. Sci. U. S. A. 89, 11046-11050). In etiolated seedlings, ACS4 is specifically induced by indoleacetic acid (IAA). The response to IAA is rapid (within 25 min) and insensitive to protein synthesis inhibition, suggesting that the ACS4 gene expression is a primary response to IAA. The ACS4 mRNA accumulation displays a biphasic dose-response curve which is optimal at 10 μM of IAA. However, IAA concentrations as low as 100 nM are sufficient to enhance the basal level of ACS4 mRNA. The expression of ACS4 is defective in the Arabidopsis auxin-resistant mutant lines axr1-12, axr2-1, and aux1-7. ACS4 mRNA levels are severely reduced in axr1-12 and axr2-1 but are only 1.5-fold lower in aux1-7. IAA inducibility is abolished in axr2-1. The ACS4 gene was isolated and structurally characterized. The promoter contains four sequence motifs reminiscent of functionally defined auxin-responsive cis-elements in the early auxin-inducible genes PS-IAA4/5 from pea and GH3 from soybean. Conceptual translation of the coding region predicts a protein with a molecular mass of 53,795 Da and a theoretical isoelectric point of 8.2. The ACS4 polypeptide contains the 11 invariant amino acid residues conserved between aminotransferases and ACC synthases from various plant species. An ACS4 cDNA was generated by reverse transcriptase-polymerase chain reaction, and the authenticity was confirmed by expression of ACC synthase activity in Escherichia coli.} }